and noting that it is satisfied initially. One problem that arises due to this treatment is the lack of a correcting mechanism in cases when the length changes slightly due to numerical errors. We implement the solution proposed by [1]} by introducing a numerical stabilisation term, recasting eq. (REF ) as
\( 0 = \partial _s{x} \cdot \partial _s{u} - w (1 - \partial _s{x} \cdot \partial _s{x}),\) 
